[添加新依赖项时软件包会卸载？

Question

在基于alpine linux-的docker的入口点脚本中，我有以下几行：

#!/bin/sh
echo "============== START ============"
echo $@
NOLOAD=0
FILE=""

RET=1

if [ !  -f /initialized ]; then
  echo "not initialized"
  apk add --virtual .init-deps bash
  echo "bash installed"
  echo "Building from server"
  apk add --virtual .init-deps git
  echo "git installed"
  bash load_git.sh "${GIT_SERVER}" "${GIT_USERNAME}" "${GIT_PASSWORD}" "${GIT_BRANCH}"
  RET=$?
  echo cloning done
fi
echo "just before purging all dependencies"
apk --purge del .init-deps

我希望安装bash，以及git并使用bash运行load_git.sh脚本。我正在文学上每隔一行记录日志，但是在load_git.sh脚本运行之前就得到了一些奇怪的结果：

============== START ============

not initialized
(1/6) Installing ncurses-terminfo-base (6.1_p20191130-r0)
(2/6) Installing ncurses-terminfo (6.1_p20191130-r0)
(3/6) Installing ncurses-libs (6.1_p20191130-r0)
(4/6) Installing readline (8.0.1-r0)
(5/6) Installing bash (5.0.11-r1)
Executing bash-5.0.11-r1.post-install
(6/6) Installing .init-deps (20200109.202215)
Executing busybox-1.31.1-r8.trigger
OK: 18 MiB in 24 packages
bash installed
Building from server
(1/12) Installing ca-certificates (20191127-r0)
(2/12) Installing nghttp2-libs (1.40.0-r0)
(3/12) Installing libcurl (7.67.0-r0)
(4/12) Installing expat (2.2.9-r1)
(5/12) Installing pcre2 (10.34-r1)
(6/12) Installing git (2.24.1-r0)
(7/12) Upgrading .init-deps (20200109.202215 -> 20200109.202216)
(8/12) Purging bash (5.0.11-r1)
Executing bash-5.0.11-r1.pre-deinstall
(9/12) Purging readline (8.0.1-r0)
(10/12) Purging ncurses-libs (6.1_p20191130-r0)
(11/12) Purging ncurses-terminfo (6.1_p20191130-r0)
(12/12) Purging ncurses-terminfo-base (6.1_p20191130-r0)
Executing busybox-1.31.1-r8.trigger
Executing ca-certificates-20191127-r0.trigger
OK: 25 MiB in 25 packages
git installed
/init.sh: line 17: bash: not found
cloning done
outside if statement to get source
just before purging all dependencies
Build failed, starting shell

我无法理解安装git也会清除bash的事实，这完全没有道理。

编辑：这仅在通过Synology nas中的ssh连接启动docker时发生，当使用本地docker镜像并在本地启动时，它工作得很好。